From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Samuel <chris@csamuel.org>
Subject: Re: multiple device usage
Date: Mon, 29 Dec 2008 22:32:05 +1100
Message-ID: <200812292232.08037.chris@csamuel.org>
References: <556243856@web.de> <200812271745.45860.chris@csamuel.org>
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On Sat, 27 Dec 2008 5:45:42 pm Chris Samuel wrote:

> I'll add two questions that're not answered by the Wiki too.. :-)

Looking at the source implies to me:

> 1) If you add a second disk to an existing btrfs filesystem, can you get =
it
> to set it up as a RAID-1 arrangement rather than just rebalancing the
> metadata and then striping ?

No, you can't, the data stripe numbers seem to be set at mkfs time.

The rebalancing code does appear (from a naive read of the code) to be able=
 to=20
rebalance over stripes, but I have no idea if the disk format currently=20
supports changing that on the fly.

> 2) With the concerns that people have about SSD reliability (hi Val :-) !)
> would it make sense to set up two equal sized partitions on the SSD and u=
se
> RAID-1 across them, or can you tell btrfs to keep multiple copies of the
> data, a la ZFS ?

Again it would appear that you need to have two partitions and that btrfs=20
cannot (at present) keep multiple data stripes on the same partition.

Could someone who actually knows the code to comment on whether my inferenc=
es=20
are accurate or not please ?  :-)

cheers,
Chris
=2D-=20
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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